U.S. Pat. No. 5,503,785 discloses an apparatus and process for making three-dimensional objects of a predetermined shape. The apparatus comprises a first dispensing head which is mounted for relative movement with respect to a second dispensing head so as to be able to deposit material in multiple passes and layers to form an object of a predetermined shape. The first dispensing head may be connected to a lift device, such as a hydraulic fluid cylinder or a spring loaded solenoid for providing relative movement of the first dispensing head with respect to the second dispensing head.
US patent application US 2015/0290861 A1 discloses a barrel for use in an additive manufacturing machine comprising a sleeve extending along a longitudinal axis; a conduit extending along the longitudinal axis through the sleeve; and an actuating system associated with the sleeve, wherein the actuating system is configured to move the conduit along the longitudinal axis relative to the sleeve between a first position and a second position. The barrel further comprises a nozzle associated with the conduit, wherein the nozzle is movable with the conduit relative to the sleeve between the first position and the second position. In an embodiment the actuating system may comprise a solenoid actuator or a servo actuator.